Bottom Line:
Semi-transparent perovskite solar cells are highly attractive for a wide range of applications, such as bifacial and tandem solar cells; however, the power conversion efficiency of semi-transparent devices still lags behind due to missing suitable transparent rear electrode or deposition process.We employ high-mobility hydrogenated indium oxide as transparent rear electrode by room-temperature radio-frequency magnetron sputtering, yielding a semi-transparent solar cell with steady-state efficiency of 14.2% along with 72% average transmittance in the near-infrared region.With such semi-transparent devices, we show a substantial power enhancement when operating as bifacial solar cell, and in combination with low-bandgap copper indium gallium diselenide we further demonstrate 20.5% efficiency in four-terminal tandem configuration.

ABSTRACTSemi-transparent perovskite solar cells are highly attractive for a wide range of applications, such as bifacial and tandem solar cells; however, the power conversion efficiency of semi-transparent devices still lags behind due to missing suitable transparent rear electrode or deposition process. Here we report a low-temperature process for efficient semi-transparent planar perovskite solar cells. A hybrid thermal evaporation-spin coating technique is developed to allow the introduction of PCBM in regular device configuration, which facilitates the growth of high-quality absorber, resulting in hysteresis-free devices. We employ high-mobility hydrogenated indium oxide as transparent rear electrode by room-temperature radio-frequency magnetron sputtering, yielding a semi-transparent solar cell with steady-state efficiency of 14.2% along with 72% average transmittance in the near-infrared region. With such semi-transparent devices, we show a substantial power enhancement when operating as bifacial solar cell, and in combination with low-bandgap copper indium gallium diselenide we further demonstrate 20.5% efficiency in four-terminal tandem configuration.

f4: Microstructure and photovoltaic performance of the semi-transparent planar perovskite solar cell.(a) The cross-sectional SEM image of the complete device. Scale bar, 1μm. (b) The transmission (T), reflection (R) and absorption (A) of semi-transparent cell. A photograph of the semi-transparent device is also shown as inset. Current density–voltage (J–V) curve (c), external quantum efficiency (EQE) spectra (d) and steady-state efficiency at maximum power point (e) of the semi-transparent planar perovskite solar cell. (f) Bifacial application of the semi-transparent cell with white paper as reflective background. The first and second dashed lines indicate the insertion and removal of the commercial white paper as reflective background, respectively. The measurement conditions in the J–V, EQE and MPP are same as in Fig. 2.

Mentions:
Figure 4 summarizes the microstructure, transmission and photovoltaic performance of a semi-transparent planar perovskite solar cell produced as described above. The cross-sectional SEM image in Fig. 4a shows a cell structure of FTO/ZnO/PCBM/CH3NH3PbI3/Spiro-OMeTAD/MoO3/In2O3:H. An electron beam-evaporated Ni-Al grid is applied for better charge carrier collection in cells with area above 0.5 cm2. The cell area is defined by mechanical scribing down to the FTO layer. The perovskite grown from 140 nm PbI2 and 45 mg ml−1 CH3NH3I solution shows a flat and dense layer with grain size comparable to the film thickness. Figure 4b displays the transmission, reflection and absorption of the semi-transparent cell. The transmission through the whole device shows a peak of 77% at 940 nm and an average of 72% between 800 and 1,150 nm. The high sub-bandgap transmission is attributed to the low free-carrier absorption in high-mobility In2O3:H (ref. 48). In addition, the photograph of the semi-transparent device in the inset of Fig. 4b shows a decent transmission in visible region as the picture behind the device can be clearly recognized. The hatched area in Fig. 4b indicates optical losses due to insufficient absorption in the perovskite layer. This means there is still much room to increase the current in the semi-transparent cell by optimizing the (optical) thickness of perovskite layer.

f4: Microstructure and photovoltaic performance of the semi-transparent planar perovskite solar cell.(a) The cross-sectional SEM image of the complete device. Scale bar, 1μm. (b) The transmission (T), reflection (R) and absorption (A) of semi-transparent cell. A photograph of the semi-transparent device is also shown as inset. Current density–voltage (J–V) curve (c), external quantum efficiency (EQE) spectra (d) and steady-state efficiency at maximum power point (e) of the semi-transparent planar perovskite solar cell. (f) Bifacial application of the semi-transparent cell with white paper as reflective background. The first and second dashed lines indicate the insertion and removal of the commercial white paper as reflective background, respectively. The measurement conditions in the J–V, EQE and MPP are same as in Fig. 2.

Mentions:
Figure 4 summarizes the microstructure, transmission and photovoltaic performance of a semi-transparent planar perovskite solar cell produced as described above. The cross-sectional SEM image in Fig. 4a shows a cell structure of FTO/ZnO/PCBM/CH3NH3PbI3/Spiro-OMeTAD/MoO3/In2O3:H. An electron beam-evaporated Ni-Al grid is applied for better charge carrier collection in cells with area above 0.5 cm2. The cell area is defined by mechanical scribing down to the FTO layer. The perovskite grown from 140 nm PbI2 and 45 mg ml−1 CH3NH3I solution shows a flat and dense layer with grain size comparable to the film thickness. Figure 4b displays the transmission, reflection and absorption of the semi-transparent cell. The transmission through the whole device shows a peak of 77% at 940 nm and an average of 72% between 800 and 1,150 nm. The high sub-bandgap transmission is attributed to the low free-carrier absorption in high-mobility In2O3:H (ref. 48). In addition, the photograph of the semi-transparent device in the inset of Fig. 4b shows a decent transmission in visible region as the picture behind the device can be clearly recognized. The hatched area in Fig. 4b indicates optical losses due to insufficient absorption in the perovskite layer. This means there is still much room to increase the current in the semi-transparent cell by optimizing the (optical) thickness of perovskite layer.

Bottom Line:
Semi-transparent perovskite solar cells are highly attractive for a wide range of applications, such as bifacial and tandem solar cells; however, the power conversion efficiency of semi-transparent devices still lags behind due to missing suitable transparent rear electrode or deposition process.We employ high-mobility hydrogenated indium oxide as transparent rear electrode by room-temperature radio-frequency magnetron sputtering, yielding a semi-transparent solar cell with steady-state efficiency of 14.2% along with 72% average transmittance in the near-infrared region.With such semi-transparent devices, we show a substantial power enhancement when operating as bifacial solar cell, and in combination with low-bandgap copper indium gallium diselenide we further demonstrate 20.5% efficiency in four-terminal tandem configuration.

ABSTRACTSemi-transparent perovskite solar cells are highly attractive for a wide range of applications, such as bifacial and tandem solar cells; however, the power conversion efficiency of semi-transparent devices still lags behind due to missing suitable transparent rear electrode or deposition process. Here we report a low-temperature process for efficient semi-transparent planar perovskite solar cells. A hybrid thermal evaporation-spin coating technique is developed to allow the introduction of PCBM in regular device configuration, which facilitates the growth of high-quality absorber, resulting in hysteresis-free devices. We employ high-mobility hydrogenated indium oxide as transparent rear electrode by room-temperature radio-frequency magnetron sputtering, yielding a semi-transparent solar cell with steady-state efficiency of 14.2% along with 72% average transmittance in the near-infrared region. With such semi-transparent devices, we show a substantial power enhancement when operating as bifacial solar cell, and in combination with low-bandgap copper indium gallium diselenide we further demonstrate 20.5% efficiency in four-terminal tandem configuration.